Circuit interrupter



June 26, 1962 c. H. BAKER 3,041,426

CIRCUIT INTERRUPTER Filed Dec. 1. 1960 2 Sheets-Sheet 1 Q3 5/ INVENTOR.22/23 B C/2045515. Bake/7 Wm WM United States Patent M 3,041,426 CIRCUITINTERRUPTER Charles H. Baker, Arlington Heights, 111., assignor to S & CElectric Company, Chicago, 111., a corporation of Delaware Filed Dec. 1,1960, Ser. No. 72,934 Claims. (Cl. 200--114) This invention relates,generally, to circuit interrupters and it has particular relation todrop out fuse cutouts of the kind and character shown in U.S. PatentNos. 2,745,921 and 2,816,979 issued, respectively, May 15, 1956, andDecember 17, 1957, and arranged to be manually manipulated by aloadbreak tool such as that shown in US. Patent No. 2,816,981, issuedDecember 17, 1957.

In the expulsion type cutout, such as shown in U.S. Patent No.2,745,921, issued May 15, 1956, as the magnitude of the currentinterrupted increases, the upward thrust on the fuse tube increases. Onelimitation in the maximum current which can be interrupted successfullyby the cutout is the strength of the fittings which support the cutout.If the upward thrust becomes too great, the supporting fittings may beforced out of their original shape and make the device unsuitable forfurther use. This is particularly true when the fusible section, wherethe arc is drawn, is located at the upper end of the fuse tube andremote from the lower open end.

'One arrangement for reducing this upward thrust in a cutout of theexpulsion type is described in U.S. Patent No. 2,816,979, issuedDecember 17, 1957. This involveslocating the fusible section in spacedrelation to the upper end of the fuse tube and nearer to the lower openend by employing a conductor, preferably in the form of a rod, whichextends into the fuse tube from the top and thus serves as the upperterminal of the fuse link at a point intermediate the ends of the fusetube rather than at the extreme upper end. By so positioning the fusiblesection nearer to the lower open end, the energy released for any givenvalue of fault current was reduced with a corresponding reduction in theupward thrust applied to the fuse tu-be tending to distort the fittings.However, as the fault current to be interrupted exceeds a predeterminedrelatively high value, even the arc shortening means provided by therod-like conductor may not limit the energy incident to circuitinterruption to such an extent that the support fittings are notdistorted.

Accordingly, among the objects of this invention are: To counteract in anew and improved manner the upward thrust on the fuse tube when it isrequired to interrupt relatively high fault current by applying adownward thrust the magnitude of which is a function of the magnitude ofthe fault current; to close the upper end of the fuse tube with a capcapable of resisting the upward thrust and holding the conductor or rodin place when the fuse blows; to provide an auxiliary exhaust passagewayat the upper end of the fuse tube and to close it by a rupturable memberarranged to vent the exhaust passageway when the fault current exceeds apredetermined value; to maintain the relative positions of the upperline contact and the pull ring on the upper fuse tube terminal whileproviding the auxiliary exhaust passageway; to position the exhaustpassageway at an angle to the bore of the fuse tube and in communicationtherewith in order to develop a downward component of thrust on the fusetube and to direct the discharge away from the upper line terminal andaway from the operator undertaking to close the fuse on a fault; and tolocate the exhaust passageway in a branch of the upper fuse tubeterminal in such position that it does not interfere with the operationof a load-break tool employed to open the fuse.

3,041,426 Patented June 26, 1962 Other objects of this invention will,in part, be obvious and in part appear hereinafter.

In the drawings:

FIG. 1 is a perspective view of a drop out fuse cutout in which thepresent invention is embodied.

FIGS. 2A and 2B, taken together, with the former placed above thelatter, show a longitudinal cross sec tional view of the fuse tube andfuse tube terminals forming a part of the fuse cutout illustrated inFIG. 1.

FIG. 3 is a view, similar to FIG. 2A, and showing a modifiedarrangement.

Referring now particularly to FIG. 1 of the drawings, it will beobserved that the reference character 9 designates a support bracketwhich constitutes one of a pair of brackets that is employed formounting devices on a cross arm carried at the upper end of a pole thatis employed for supporting an electrical transmission line. The supportbracket 9 is arranged to carry an insulator mount ing as indicated,generally, at 10 which may be of the type shown in U.S. Patent No.2,606,954, issued August 12, 1952. It will be understood, however, thatother insulator mountings can be employed in practicing the presentinvention. The insulator mounting 10 includes a rearwardly extendingsupport arm 11 which is, secured, as shown, to the lower forwardlyextending portion of the support bracket 9 and an insulator 12. Upperand lower metallic terminal supports 13 and 14 are provided, as shown,at the upper and lower ends of the insulator 12. The metallic terminalsupports 13 and 14 extend forwardly of the insulator 12 which,preferably, is formed of porcelain. These terminal supports carry,respectively, upper and lower line terminal members 15 and 16 and a fusetube that is indicated, generally, at 17. In accordance withconventional practice the fuse tube 17 is removable and is arranged todrop out upon the occurrence of an overload suflicient to cause the fuselink therein to blow. At its lower end the fuse tube 17 is provided witha lower fuse terminal assembly, shown generally at 18, that is pivotallyand slidably mounted on the lower line terminal member 16. At its upperend the :fuse tube 17 has an upper fuse terminal assembly, showngenerally at 19, which cooperates with the upper line terminal member15.

The lower line terminal member 16 comprises a hinge casting, showngenerally 'at 22, that is formed of suitable good conducting metal, suchas brass, and has an inverted' U-shape. It is secured by a bolt 23 tothe terminal support 14 at the lower end of the insulator 12. A splitbolt connector 24 extends rearwardly from the hinge casting 22 andserves to receive a line conductor. At the opposite end of the hingecasting 22, slots 25 are provided in the opposite sides 22 for slida-blyand pivotally receiving trunnions 26 that extend from opposite sides ofa toggle member 27 through which a shaft 28 extends. The toggle member27 is preferably formed of a brass casting and a more detaileddescription of its construction and operation is set forth in US. PatentNo. 2,553,098, issued May 15, 1951. The toggle member 27 is pivotallysecured by a hinge pin 29 to arms 30 that extend rearwardly from a lowerbrass ferrule 31 which forms a part of the lower fuse tube terminalassembly 18.

As shown more clearly in FIG. 2B of the drawings, a flipper 34 isrocka-bly mounted on the shaft 28. As described in US. Patent No.2,553,098, issued May 15, 1951, the flipper 34, biased by a spring, isarranged to withdraw the flexible lead of a fuse link from the fuse tube17 and also is arranged to keep the toggle linkage, of which the togglemember 27 forms a part, in the operative position until the fuse linkblows. For this latter purpose the flipper 34 has a shoulder 35 which isarranged to engage a shoulder 36 on a detent 37 that extends rearwardlyfrom the lower ferrule 31.

Within the fuse tube 17, as shown in FIGS. 2A and 213, there is provideda fuse link 38 of conventional construction which has a flexible lead 39extending therefrom and out of the lower end of the fuse tube 17. Itwill be observed that the lower end of the flexible lead 39 extends overthe flipper 34 and, as long as the fuse link 38 remains intact, itserves to hold the flipper 34 in the position where the shoulder 35engages the shoul der 36. The extreme lower end of the flexible lead 39extends around a stud 40 and is clamped securely thereto by a clamp nut41.

The toggle member 27 has an eye portion 42 that is arranged to receive aprong of a switch stick. The purpose of this is to facilitate thehandling of the fuse tube 17 for removing it from the mounting andreplacing the same.

As illustrated in FIG. 2A the upper fuse terminal assembly 19 includes aferrule 43, preferably formed of brass, which has an extension 44 at itsupper end that provides a passageway 45 which constitutes an extensionof the bore or passageway 46 in the fuse tube 17. The upper end of theextension 44, which is integral with the ferrule 43, is closed by athreaded cap 47 which may be formed integrally with a stud or rod-likeconductor 48. Instead of forming the stud or rod-like conductor 48integrally with the threaded cap 47, it may be formed separately asdescribed in U.S. Patent No. 2,816,979, issued December 17, 1957. Ifdesired, the stud or rodlike conductor 48 can be extended to positionits lower end well below the lower end of the ferrule 43 for voltagestress distribution purposes. As set forth in this patent, the stud orrod-like conductor 48 is provided for receiving a threaded portion 49 ofa fuse link terminal 50 located at the upper end of the fuse link 38 forthe purpose of locating the fusible section 38 nearer to the lower openend of the fuse tube 17 with the result that the energy incident toblowing of the fuse link 38 is reduced and thus there is a correspondingreduction in the upward thrust applied to the fuse tube 17. It will beunderstood that the threaded cap 47 is a reusable cap and that it isadapted to hold closed the passageway 45 under all operating conditionswithin the capability of the fuse tube 17 for handling fault currents.An eye portion 51 is formed integrally with the ferrule 43 for receivingthe prong of a switch stick or one of the terminals of a loadbreak tool.

The threaded cap 47 has a convex head 52 that engages the underside of aseat 53 formed integrally in the lower arm of a U-shaped top contact 54as shown in FIG. 1. A top contact strip 55 is connected by rivets 56 tothe upper arm of the top contact 54. At its rear end the contact strip55 is positioned underneath a leg of an I-shaped terminal pad 58 whichcarries a split bolt connector 59 for receiving the other lineconductor. A bolt 60 extends through the terminal support 13 togetherwith the contact strip 55 to hold these elements securely in position.

With a view to providing a relatively stiff spring for resisting theupward thrust of the fuse tube 17, there is provided a recoil bar 63that is clamped by the bolt 60 to the terminal support 13. The recoilbar 63 extends forwardly in cantilever fashion over the upper end of thefuse tube 17. Preferably the recoil bar 63 is formed of magneticmaterial such as cold rolled steel. Near the outer end of the recoil bar63 there is a tapped opening for receiving a hollow threaded bushing 64as described in more detail in US. Patent No. 2,745,923, issued May 15,1956. The bushing 64 is screwed into the recoil bar 63 and a portionprojects above it for receiving a lock nut 65. It is desirable tointerconnect the rearwardly extending arms of the U shaped top contact54. For this purpose a contact stud 66 is employed. -It is formed ofgood conducting material, such as brass, and its upper end 67 extendsthrough the upper arm of the top contact 54 and is headed over Within asuitable opening in the forward'end of the contact strip 55. A coilcompression spring 71 reacts downwardly against the seat 53 and isdisposed coaxially with the contact stud 66 which islocated to becoaxial with the vertical axis of the fuse tube 17. The upper end of thecoil compression spring 71 extends around the lower end of the hollowbushing 64 and bears against the underside of the outer end of therecoil bar 63. The coil compression spring 71 is held in prestressedcondition by the contact stud 66 and can be readily further stressed ascompared to the recoil bar 63 so that the initial upward movement of thefuse tube 17 acts first to compress further the spring 71 withoutcausing any substantial upward movement of the outer end of the recoilbar 63. When only relatively small fault current is required to beinterrupted, only the coil compression spring 73 will be stressed to anyappreciable extent.

An L-shaped reinforcing bar 72 is mounted on the underside of the recoilbar 63 and below the terminal support 13. The horizontal arm 73 of thereinforcing bar 72 extends underneath the terminal support 13 and issecured thereto by the bolt 60. The downwardly extending arm. 74 of thereinforcing bar 72 extends parallel to the vertical axis of the fusetube 17 and is positioned rearwardly thereof between it and theinsulator 12. Under certain conditions it is desired that there beconjoint movement of the reinforcing bar 72 and the re coil bar 63. Forthis purpose a pin 75 is employed.

At the lower end of the downwardly extending arm 74 there is provided acombination guideand anchor that is shown, generally, at 79. Thecombination guide and anchor 79 includes forwardly extending arms 80 atthe outer ends of which are rearwardly curved arms 81. The forwardlyextending arms 80 serve to guide the upper fuse terminal assembly 19 orthe fuse tube 17 into proper position generally regardless of thedirection from which force is applied to the eye portion 51 that isformed in tegrally with the ferrule 43 to swing the fuse tube 17 to theclosed position so that the threaded cap 47 will reg ister with the seat53. Preferably the combination guide and anchor 79 is formed of goodconducting material, such as brass, since it may be called upon toconduct current when the fuse tube 17 is moved out of the circuit closedposition while it is carrying load current as de scribed in more detailin US. Patent No. 2,816,981, issued December 17, 1957, by the use of theloadbreak tool described in this patent.

When the fuse link 38 is assembled in the fuse tube 17 as describedhereinbefore with the flexible lead 39 overlying the flipper 34 andclamped to the toggle member 27 by the clamp nut 4-1, the shoulder 35 isheld in engagement with the shoulder 36 and a rigid construction isprovided that can be handled as a unit. The prong of a live line tool orswitch stick is inserted in the eye 42 and the fuse tube 17 is lifted toposition the trunnions 26 in the slots 25. When so manipulated, the fusetube 17 hangs downwardly and the trunnions 26 occupy positions at thebottoms of the slots 25. Then the prong of the live line tool or switchstick is inserted in the eye portion 51 and the fuse tube 17 is swungupwardly to the position shown in FIG. 1 which is the closed position.

When it is desired to move the fuse tube 17 to the open position whileit is carrying load current, a loadbreak tool, constructed as describedin US. Patent No. 2,816,- 981, issued December 17, 1957, can be used.One terminal of the loadbreak tool is caused to engage one or the otherof the rearwardly curved arms 81 of the combination guide and anchor 79while another terminal of the loadbreak tool engages the eye portion 51,Then the loadbreak tool is operated to separate the upper fuse terminalassembly 19 from the upper line terminal member 15 and to shunt the loadcurrent through the loadbreak tool. On subsequent manipulation of theloadbreak tool, this current flow is interrupted within the tool andwithout external arcing. Thereafter, the terminals of the loadbreak tooare detached from the combination guide and r anchor 79 and from the eyeportion 51 leaving the fuse tube 17 in the open pendant position.

It was pointed out hereinbefore that the use of the stud or rod-likeconductor 48 serves to position the fuse link 38 at a locationrelatively closer to the open lower end of the fuse tube 17 than if itwere placed at the extreme upper end. Because of this positioning of thefuse link, the energy released on blowing of the fuse link 38 is reducedand there is a corresponding reduction in the upward thrust applied tothe fuse tube 17. However, as the fuse cutouts of this type are calledupon to interrupt higher and higher fault currents, it has been foundthat, even when the rod-like conductor 48 is employed, still the upwardthrust on the fuse tube 17 may be such that on interruption ofexceedingly high fault currents the upper and lower fuse terminalmembers 15 and 16 are deformed along with deformation of the upperterminal member 15.

In accordance with this invention provision is made for counteractingthis upward thrust by providing a downward thrust which is a function ofthe magnitude of the fault current. For this purpose a branch 82 isformed integrally with the upper fuse terminal assembly 19 and it has anexhaust passageway 93 extending therethrough at an angle to thepassageway 45 and bore or passageway 46 in the fuse tube 17. In thearrangement shown, the angle of inclination is 45. The outer end of thebranch 82 is threaded for receiving a threaded expendable cap 84 whichis provided with an annular slot 85 thereby forming a weakened centralsection 86 that is arranged to be blown out when it is subjected topredetermined pressure.

In operation, when the fuse link 38 blows under relatively low faultcurrent conditions, only the coil compression spring 71 is stressedsufficiently to permit the fuse tube 17 to move upwardly, n theinterruption of a still higher fault current, the thrust on the fusetube may be such as to further stress the recoil bar 63 and move itupwardly. Under these assumed conditions the fuse tube 17 is vented onlyat its lower end. However, should the device be subjected to anextremely heavy fault current that otherwise would cause the fuse tube17 to move upwardly through an extent likely to damage the lower andupper fuse terminal assemblies 18 and 19 and the upper terminal member15, the pressure under these circumstances within the upper fuseterminal assembly 19 is sufficient to rupture the expendable cap 84 andblow out the central section 86. The fuse tube 17 is vented at the upperend at an angle to the vertical axis with the result that there is adownward component of force developed which acts in a direction oppositeto the upward thrust applied to the fuse tube 17. The fuse tube 17 isnot moved upwardly as far as it otherwise might be. Within thecapabilities of the device to interrupt fault current the upwardmovement of the fuse tube 17 is reduced together with the likelihood ofdamage to the terminal fittings.

It will be observed that the branch 82 providing the exhaust passageway83 is directed outwardly and upwardly away from the upper terminalmember This directs the products of the arc blast away from the upperterminal member 15 and also away from the operator located on the groundshould he close the fuse tube 17 on a fault of a magnitude suflicient torupture the expendable cap 84.

In some instances it may be desirable to locate the fuse link 38 at theextreme upper end of the fuse tube 17. Such an arrangement isillustrated in FIG. 3 where a removable button head 90 is threaded ontothe threaded portion 49 of the fuse link terminal 50, Here the threadedcap 47 serves only to clamp the button head 90 in place on the upper endof the extension 44 of the upper fuse terminal assembly 19 and to holdclosed the passageway 45 under all fault currents within thecapabilities of the device to interrupt,

What is claimed as new is:

1. In a device for interrupting a high voltage electric 6 power circuiton flow therein of relatively small or relatively great fault current,in combination, a fuse tube open at one end, a terminal closing theother end of said fuse tube and capable of maintaining it closed on interruption of fault current within the range of capability of thedevice, said terminal including a rod-like conductor extending therefromalong the axis of said fuse tube toward said open end and adapted toreceive at its inner end one terminal of a replaceable fuse link theother terminal of which extends out of said open end of said fuse tube,means providing an exhaust passageway transverse to and communicating atits inner end with the opening through said fuse tube at said other endand intermediate the ends of said rod-like conductor, and rupturablemeans closing off the outer end of said exhaust passageway and capableof withstanding the pressure generated within said fuse tube on blowingof the fuse link to interrupt the flow of relatively small fault currentand adapted to rupture and vent said fuse tube at said other end onblowing of the fuse link to interrupt the flow of relatively great faultcurrent.

2. In a fuse construction, in combination, a pair of line terminals ininsulated spaced relation, a fuse tube having a fuse terminal at one endand open at the other end, said fuse terminal being normally connectedto one of said line terminals, a conductor extending through said fusetube; said conductor including in series a rodlike section connected tosaid fuse terminal, a fusible section, and a flexible section connectedto the other line terminal; a metallic cap threaded on said fuseterminal to hold said rod-like section in circuit therewith and closesaid one end of said fuse tube, the connection of said fuse terminal tosaid one 'line terminal being through said metallic cap, said fuseterminal having an exhaust passageway communicating at its inner endwith the opening through said fuse tube and having the outer end openingin a direction away from said metallic cap and said one line terminal,and rupturable means closing off said exhaust passageway whereby saidfuse tube is vented at said one end thereof when a predeterminedpressure is generated therein on blowing of said fusible section.

3. A device for interrupting a high voltage electric power circuit onflow therein of relatively small or relatively great fault currentcomprising, in combination, insulator means, upper and lower lineterminals etxending laterally from said insulator means, a fuse tubeopen at its lower .end, upper and lower fuse terminals on said fuse tubeengaging said upper and lower line terminals respectively, said upperfuse terminal closing the upper end of said fuse tube and capable ofmaintaining it closed on interruption of fault current within the rangeof capability of the device, conductor means including a fusible sectioninterconnecting said fuse terminals and adapted on flow of fault currentto generate substantial pressure acting against said upper fuse terminalto move said fuse tube upwardly with a force that increases with themagnitude of the fault current, branch means on said upper fuse terminalproviding an exhaust passageway inclined upwardly to and communicatingat its inner end with the opening through said fuse tube at its upperend and directed away from said upper line terminal, and rupturablemeans closing off said exhaust passageway and capable of withstandingthe pressure generated within said fuse tube on blowing of said fusiblesection to interrupt the flow of relatively small fault current andadapted to rupture and vent said fuse tube at its upper end on blowingof said fusible section to interrupt the flow of relatively great faultcurrent and cause the application of a force component to said fuse tubeacting in a direction opposite to said force that moves said fuse tubeupwardly.

4. A device for interrupting a high voltage electric power circuit onflow therein of relatively small or relatively great fault currentcomprising, in combination, insulator means, upper and lower lineterminals extending laterally from said insulator means, a fuse tubeopen at its lower end, upper and lower line terminals respectively, saidupper fuse terminal including a reusable cap closing the upper end ofsaid fuse tube and capable of maintaining it closed on interruption offault current Within the range of capability of the device, conductormeans including a fusible section interconnecting said fuse terminalsand adapted on flow of fault current to generate substantial pressureacting against said upper fuse terminal to move said fuse tube upwardlywith a force that increases with the magnitude of the fault current,said upper fuse terminal having an exhaust passageway inclined upwardlyto and communicating at its inner end with the opening through said fusetube and directed away from said upper line terminal, and an expendablecap threaded on said upper fuse terminal and closing off said exhaustpassageway, said expendable cap having a frangible portion capable ofwithstanding the pressure generated within said fuse tube on blowing ofsaid fusible section to interrupt the flow of relatively small faultcurrent and adapted to rupture and vent said fuse tube at its upper endon blowing of said fusible section to interrupt the flow of relativelygreat fault current and cause the application of a force component tosaid fuse tube acting in a direction opposite to said force that movessaid fuse tube upwardly.

5. A device for interrupting a high voltage electric power circuit onflow therein of relatively small or relatively great fault currentcomprising, in combination, insulator means, upper and lower lineterminals extending laterally from said insulator means, a fuse tubeopen at its lower end, upper and lower fuse terminals on said fuse tubeengaging said upper and lower line terminals respectively, said upperfuse terminal including a reusable cap closing the upper end of saidfuse tube and capable of maintaining it closed on interruption of faultcurrent within the range of capability of the device, conducting meansextending through said fuse tube; said conductor means including inseries a rod-like section connected to said upper fuse terminal and heldin position by said reusable cap, a fusible section, and a flexiblesection connected to said lower fuse terminal; said fusible sectionbeing adapted on flow of fault current to generate substantial pressureacting against said upper fuse terminal to move said fuse tube upwardlywith a force that increases the magnitude of the fault current, meansproviding an exhaust passageway inclined upwardly to and communicatingat its inner end with the opening through said fuse tube and directedaway from said upper line terminal and said reusable cap, and anexpendable cap threaded on said upper fuse terminal and closing off saidexhaust passageway, said expendable cap having a fran- References Citedin the fileof this patent UNITED STATES PATENTS 2,109,090 Pittman et alFeb. 22, 1938 2,721,242 Curtis et al. Oct. 18, 1955 2,798,133 CurtisJuly 2 1957 2,816,979 Lindell Dec. 17, 1957 2,846,544 Wood Aug. 5, 1958

